宇宙物理学研究系

関本 裕太郎

セキモト ユウタロウ  (Yutaro SEKIMOTO)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系
東京大学 大学院理学系研究科 天文学専攻

J-GLOBAL ID
200901049964309113
researchmap会員ID
5000001980

外部リンク

主要な論文

 147
  • Ryo Nakano, Hayato Takakura, Yutaro Sekimoto, Junji Inatani, Masahiro Sugimoto, Shugo Oguri, Frederick Matsuda
    Journal of Astronomical Telescopes, Instruments, and Systems 9(02) 2023年4月19日  
  • Hayato Takakura, Yutaro Sekimoto, Junji Inatani, Shingo Kashima, Masahiro Sugimoto, Ryo Nakano, Ryo Nagata
    Journal of Astronomical Telescopes, Instruments, and Systems 9(02) 2023年4月12日  
  • E Allys, K Arnold, J Aumont, R Aurlien, S Azzoni, C Baccigalupi, A J Banday, R Banerji, R B Barreiro, N Bartolo, L Bautista, D Beck, S Beckman, M Bersanelli, F Boulanger, M Brilenkov, M Bucher, E Calabrese, P Campeti, A Carones, F J Casas, A Catalano, V Chan, K Cheung, Y Chinone, S E Clark, F Columbro, G D’Alessandro, P de Bernardis, T de Haan, E de la Hoz, M De Petris, S Della Torre, P Diego-Palazuelos, M Dobbs, T Dotani, J M Duval, T Elleflot, H K Eriksen, J Errard, T Essinger-Hileman, F Finelli, R Flauger, C Franceschet, U Fuskeland, M Galloway, K Ganga, M Gerbino, M Gervasi, R T Génova-Santos, T Ghigna, S Giardiello, E Gjerløw, J Grain, F Grupp, A Gruppuso, J E Gudmundsson, N W Halverson, P Hargrave, T Hasebe, M Hasegawa, M Hazumi, S Henrot-Versillé, B Hensley, L T Hergt, D Herman, E Hivon, R A Hlozek, A L Hornsby, Y Hoshino, J Hubmayr, K Ichiki, T Iida, H Imada, H Ishino, G Jaehnig, N Katayama, A Kato, R Keskitalo, T Kisner, Y Kobayashi, A Kogut, K Kohri, E Komatsu, K Komatsu, K Konishi, N Krachmalnicoff, C L Kuo, L Lamagna, M Lattanzi, A T Lee, C Leloup, F Levrier, E Linder, G Luzzi, J Macias-Perez, T Maciaszek, B Maffei, D Maino, S Mandelli, E Martínez-González, S Masi, M Massa, S Matarrese, F T Matsuda, T Matsumura, L Mele, M Migliaccio, Y Minami, A Moggi, J Montgomery, L Montier, G Morgante, B Mot, Y Nagano, T Nagasaki, R Nagata, R Nakano, T Namikawa, F Nati, P Natoli, S Nerval, F Noviello, K Odagiri, S Oguri, H Ohsaki, L Pagano, A Paiella, D Paoletti, A Passerini, G Patanchon, F Piacentini, M Piat, G Pisano, G Polenta, D Poletti, T Prouvé, G Puglisi, D Rambaud, C Raum, S Realini, M Reinecke, M Remazeilles, A Ritacco, G Roudil, J A Rubino-Martin, M Russell, H Sakurai, Y Sakurai, M Sasaki, D Scott, Y Sekimoto, K Shinozaki, M Shiraishi, P Shirron, G Signorelli, F Spinella, S Stever, R Stompor, S Sugiyama, R M Sullivan, A Suzuki, T L Svalheim, E Switzer, R Takaku, H Takakura, Y Takase, A Tartari, Y Terao, J Thermeau, H Thommesen, K L Thompson, M Tomasi, M Tominaga, M Tristram, M Tsuji, M Tsujimoto, L Vacher, P Vielva, N Vittorio, W Wang, K Watanuki, I K Wehus, J Weller, B Westbrook, J Wilms, B Winter, E J Wollack, J Yumoto, M Zannoni
    Progress of Theoretical and Experimental Physics 2023(4) 2022年11月21日  
    Abstract LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun–Earth Lagrangian point L2, where it will map the cosmic microwave background polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of $2.2\, \mu$K-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions, and synergies with other projects.
  • Shugo Oguri, Tadayasu Dotani, Masahito Isshiki, Shota Iwabuchi, Tooru Kaga, Frederick T. Matsuda, Yasuyuki Miyazaki, Baptiste Mot, Ryo Nagata, Katsuhiro Narasaki, Hiroyuki Ogawa, Toshiaki Okudaira, Kimihide Odagiri, Thomas Prouve, Gilles Roudil, Yasutaka Satoh, Yutaro Sekimoto, Toyoaki Suzuki, Kazuya Watanuki, Seiji Yoshida, Keisuke Yoshihara
    Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave 2022年8月27日  
  • Hayato Takakura, Ryo Nakano, Yutaro Sekimoto, Junji Inatani, Masahiro Sugimoto, Frederick T. Matsuda, Shugo Oguri
    Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave 2022年8月27日  
  • Kimihide Odagiri, Masaru Saijo, Keisuke Shinozaki, Frederick Matsuda, Shugo Oguri, Toyoaki Suzuki, Hiroyuki Ogawa, Yutaro Sekimoto, Tadayasu Dotani, Kazuya Watanuki, Ryo Sugimoto, Keisuke Yoshihara, Katsuhiro Narasaki, Masahito Isshiki, Seiji Yoshida, Thomas Prouve, Jean-Marc Duval, Keith L. Thompson
    SPACE TELESCOPES AND INSTRUMENTATION 2022: OPTICAL, INFRARED, AND MILLIMETER WAVE 12180 2022年  
    LiteBIRD is a JAXA-led international project that aims to test representative inflationary models by performing an all-sky cosmic microwave background radiation (CMB) polarization survey for 3 years at the Sun-Earth Lagrangian point L2. We aim to launch LiteBIRD in the late 2020s. The payload module (PLM) is mainly composed of the Low-Frequency Telescope (LFT), the Mid-Frequency Telescope and High-Frequency Telescope (MHFT), and a cryo-structure. To conduct the high-precision and high-sensitivity CMB observations, it is required to cool the telescopes down to less than 5 K and the detectors down to 100 mK. The high temperature stability is also an important design factor. It is essential to design and analyze the cryogenic thermal system for PLM. In this study, the heat balance, temperature distribution, and temperature stability of the PLM for the baseline design are evaluated by developing the transient thermal model. The effect of the Joule-Thomson (JT) coolers cold tip temperature variation, the periodical changes in subK Adiabatic Demagnetization Refrigerator (ADR) heat dissipation, and the satellite spin that generates the variable direction of solar flux incident are implemented in the model. The effect of contact thermal conductance in the LFT and the emissivity of the V-groove on the temperature distribution and heat balance are investigated. Based on the thermal analysis, it was confirmed that the PLM baseline design meets the requirement of the temperature and the cooling capability of the 4K-JT cooler. In addition, the temperatures of the V-groove and the LFT 5-K frame are sufficiently stable for the observation. The temperature stability of the Low Frequency Focal Plane (LF-FP) is also discussed in this paper.
  • Y. Sekimoto, P. A.R. Ade, A. Adler, E. Allys, K. Arnold, D. Auguste, J. Aumont, R. Aurlien, J. Austermann, C. Baccigalupi, A. J. Banday, R. Banerji, R. B. Barreiro, S. Basak, J. Beall, D. Beck, S. Beckman, J. Bermejo, P. De Bernardis, M. Bersanelli, J. Bonis, J. Borrill, F. Boulanger, S. Bounissou, M. Brilenkov, M. Brown, M. Bucher, E. Calabrese, P. Campeti, A. Carones, F. J. Casas, A. Challinor, V. Chan, K. Cheung, Y. Chinone, J. F. Cliche, L. Colombo, F. Columbro, J. Cubas, A. Cukierman, D. Curtis, G. D'Alessandro, N. Dachlythra, M. De Petris, C. Dickinson, P. Diego-Palazuelos, M. Dobbs, T. Dotani, L. Duband, S. Duff, J. M. Duval, K. Ebisawa, T. Elleflot, H. K. Eriksen, J. Errard, T. Essinger-Hileman, F. Finelli, R. Flauger, C. Franceschet, U. Fuskeland, M. Galloway, K. Ganga, J. R. Gao, R. Genova-Santos, M. Gerbino, M. Gervasi, T. Ghigna, E. Gjerløw, M. L. Gradziel, J. Grain, F. Grupp, A. Gruppuso, J. E. Gudmundsson, T. De Haan, N. W. Halverson, P. Hargrave, T. Hasebe, M. Hasegawa, M. Hattori, M. Hazumi, S. Henrot-Versille, D. Herman, D. Herranz, C. A. Hill, G. Hilton, Y. Hirota, E. Hivon, R. A. Hlozek, Y. Hoshino, E. De La Hoz, J. Hubmayr, K. Ichiki, T. Iida, H. Imada, K. Ishimura, H. Ishino, G. Jaehnig, T. Kaga, S. Kashima, N. Katayama
    Proceedings of SPIE - The International Society for Optical Engineering 11453 2020年  
    © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of-56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT: 34-161 GHz), one of LiteBIRD's onboard telescopes. It has a wide field-of-view (18° x 9°) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90a-▪ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented.
  • Tom Nitta, Makoto Nagai, Yosuke Murayama, Ryotaro Hikawa, Ryuji Suzuki, Yutaro Sekimoto, Hayato Takakura, Takashi Hasebe, Kazufusa Noda, Satoshi Saeki, Hiroshi Matsuo, Nario Kuno, Naomasa Nakai
    Proceedings of SPIE - The International Society for Optical Engineering 11453 2020年  
    © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. We are developing a 100-GHz band 109-pixel MKID camera for the Nobeyama 45-m telescope. The camera optics contains plano-convex silicon (Si) lenses with 300-and 154-mm diameters located at the 4-K and 1-K stages, and a vacuum window of 320-mm diameter. Antireflective subwavelength structures (SWSs) for the Si lenses and the vacuum window were designed to reduce surface reflection. Cyclo olefin polymer (COP) was chosen as the base material for vacuum window as the dielectric loss is comparable with high-density polyethylene and it is easy to fabricate. Antireflective SWSs optimized for 100-GHz band were simulated using ANSYS HFSS. A one-layer rectangular pillar was designed for a Si lens of 300-mm diameter and a 320-mm diameter COP window to examine the fabrication process in large areas. For 154-mm diameter Si lens, a 1.2-mm depth tapered structure was used to obtain broadband characteristics. These designed structures were fabricated on both sides using a three-Axis numerically-controlled machine. An end mill and a metal-bonded dicing blade were used for cutting the COP and Si, respectively. W-band vector network analyzer was used for S-parameter measurements of the SWS formed flat surface at an ambient temperature. Average surface reflectance of Si lenses and transmittance of the COP window in the 90-110 GHz range were found at approximately 1% and 98%, respectively.
  • Hayato Takakura, Yutaro Sekimoto, Junji Inatani, Shingo Kashima, Hiroaki Imada, Takashi Hasebe, Toru Kaga, Yoichi Takeda, Norio Okada
    IEEE Transactions on Terahertz Science and Technology 9(6) 598-605 2019年11月  査読有り
    © 2019 IEEE. Polarization of the cosmic microwave background (CMB) has crucial information on the inflationary universe. To detect these signals, it is necessary to suppress far sidelobes of a telescope, which contaminate the CMB signals with strong foreground radiation, such as the Galactic plane. LiteBIRD is the only funded CMB observation satellite for the 2020s, and the low frequency telescope (LFT; 34-161 GHz) is one of its telescopes. We measured near-field antenna patterns of the LFT using its 1/4-scaled model and examined far sidelobes up to 60° from the peaks. To cover the 20° field of view of the LFT, we investigated the antenna patterns at the edges of the focal plane as well as at the center. The measurement frequencies were 140-220 GHz, which correspond to the lowest bands (35-55 GHz) of the full-scale LFT. The measurements were consistent with the simulated far-sidelobe patterns at least -50 dB level, and showed that far sidelobes for two orthogonal polarization directions are consistent with each other down to -40 dB level. We also measured the cross-polarization patterns, and their peak level was less than -20 dB.
  • Takashi Hasebe, Yutaro Sekimoto, Tadayasu Dotani, Kazuhisa Mitsuda, Keisuke Shinozaki, Seiji Yoshida
    Journal of Astronomical Telescopes, Instruments, and Systems 5(4) 2019年10月1日  査読有り
    © 2019 Society of Photo-Optical Instrumentation Engineers (SPIE). Radiative cooling with thermal isolation shields can provide a reliable cooling system for instruments onboard satellites in orbit. We report the optimization study for the cryogenic architecture of the LiteBIRD satellite using radiative cooling. A trade study that changed the number of thermal shields and shield emissivity were conducted. The heat flow from 300 to 4.5 K, including active cooling by mechanical cryocoolers, was evaluated among the trade designs. We found that the design that consists of low-emissivity four-layer thermal shields is optimum in terms of thermal performance and system design. The optimum design achieved a heat load of 29.9 mW for the 4.5-K cooling stage, whereas the requirement was 30 mW with the assumed cryogenic system.
  • Y. Sekimoto, P. Ade, K. Arnold, J. Aumont, J. Austermann, C. Baccigalupi, A. Banday, R. Banerji, S. Basak, S. Beckman, M. Bersanelli, J. Borrill, F. Boulanger, M. L. Brown, M. Bucher, E. Calabrese, F. J. Casas, A. Challinor, Y. Chinone, F. Columbro, A. Cukierman, D. Curtis, P. De Bernardis, M. De Petris, M. Dobbs, T. Dotani, L. Duband, J. M. Duval, A. Ducout, K. Ebisawa, T. Elleot, H. Eriksen, J. Errard, R. Flauger, C. Franceschet, U. Fuskeland, K. Ganga, R. J. Gao, T. Ghigna, J. Grain, A. Gruppuso, N. Halverson, P. Hargrave, T. Hasebe, M. Hasegawa, M. Hattori, M. Hazumi, S. Henrot-Versille, C. Hill, Y. Hirota, E. Hivon, T. D. Hoang, J. Hubmayr, K. Ichiki, H. Imada, H. Ishino, G. Jaehnig, H. Kanai, S. Kashima, Y. Kataoka, N. Katayama, T. Kawasaki, R. Keskitalo, A. Kibayashi, T. Kikuchi, K. Kimura, T. Kisner, Y. Kobayashi, N. Kogiso, K. Kohri, E. Komatsu, K. Komatsu, K. Konishi, N. Krachmalnicoff, L. C. Kuo, N. Kurinsky, A. Kushino, L. Lamagna, T. A. Lee, E. Linder, B. Maffei, M. Maki, A. Mangilli, E. Martinez-Gonzalez, S. Masi, T. Matsumura, A. Mennella, Y. Minami, K. Mistuda, D. Molinari, L. Montier, G. Morgante, B. Mot, Y. Murata, A. Murphy, M. Nagai, R. Nagata, S. Nakamura, T. Namikawa, P. Natoli
    Proceedings of SPIE - The International Society for Optical Engineering 10698 2018年  査読有り
    © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. LiteBIRD is a candidate for JAXA's strategic large mission to observe the cosmic microwave background (CMB) polarization over the full sky at large angular scales. It is planned to be launched in the 2020s with an H3 launch vehicle for three years of observations at a Sun-Earth Lagrangian point (L2). The concept design has been studied by researchers from Japan, U.S., Canada and Europe during the ISAS Phase-A1. Large scale measurements of the CMB B-mode polarization are known as the best probe to detect primordial gravitational waves. The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of r < 0:001. A 3-year full sky survey will be carried out with a low frequency (34 - 161 GHz) telescope (LFT) and a high frequency (89 - 448 GHz) telescope (HFT), which achieve a sensitivity of 2.5 μK-arcmin with an angular resolution 30 arcminutes around 100 GHz. The concept design of LiteBIRD system, payload module (PLM), cryo-structure, LFT and verification plan is described in this paper.
  • Tomonori Tamura, Takashi Noguchi, Yutaro Sekimoto, Wenlei Shan, Naohisa Sato, Yoshizo Iizuka, Kazuyoshi Kumagai, Yasuaki Niizeki, Mikio Iwakuni, Tetsuya Ito
    IEEE Transactions on Applied Superconductivity 25(3) 2015年6月1日  査読有り
    © 2002-2011 IEEE. We developed SIS mixers for Atacama large millimeter/submillimeter array (ALMA) Band 8 (385-500 GHz) receiver cartridges and evaluated their performance. DC IV curves of the SIS mixers showed small leakage current at the high current density. The current density and quality factor (R-{sg}/R-{n}) of the Band 8 SIS junction were 13 \hbox{kA/cm}{2} and approximately 20, respectively. Double-sideband noise temperature of the 266 SIS mixers was 92.8 K at 4.0 K bath temperature on the average from 385 to 500 GHz with a standard deviation of 7.0%. A couple of sideband-separating (2SB) mixers for dual polarizations were used in the Band 8 receiver cartridge. The 73 receivers have met ALMA specifications of the noise temperature. Single-sideband noise temperature and image rejection ratio of the receivers were 139.5 K and 20.5 dB on the average from 385 to 500 GHz, respectively. These test results of the receivers indicate high quality and uniformity of the 2SB mixers.

MISC

 206

講演・口頭発表等

 78

担当経験のある科目(授業)

 2

共同研究・競争的資金等の研究課題

 8

産業財産権

 3

社会貢献活動

 1

● 指導学生等の数

 1
  • 年度
    2021年度(FY2021)
    博士課程学生数
    1
    修士課程学生数
    1
    インターンの人数
    9

● 指導学生の表彰・受賞

 1
  • 指導学生名
    高倉隼人
    所属大学
    東京大学
    受賞内容(タイトル、団体名等)
    B-mode from space
    受賞年月日
    2019-12-5

● 専任大学名

 1
  • 専任大学名
    東京大学(University of Tokyo)